Riveted joints are already known and used for the joining of workpieces, especially sheets of metal, and particularly when the workpieces to be joined are accessible from only one side. Typical uses of the riveted joint are the assembly of metal fittings, walls of cassettes or disk holders or border parts on insulation panels in industry and in the construction of large halls or gymnasiums. The sheet metal pieces to be joined are of a thickness of approximately 0.1 mm to approximately 3 mm, and of typically approximately 0.75 mm.
For the mounting of the rivet, made up of a rivet jacket and a rivet pin guided through the rivet jacket, the workpieces are first penetrated through a bore hole in the workpieces. The rivet with rivet jacket is pressed forward and through as far as impact of the striking head of the rivet jacket on the edge of the borehole. For production of the riveted joint between the workpieces then with holding back of the striking head, the rivet pin is drawn counter to the pressing-in direction. The end of the rivet jacket lying opposite the striking head is thereby deformed, allowing for the formation of a widened out part, so that the workpieces to be joined together are held together between the striking head and the widening out which has been produced.
This type of rivet is frequently also called a xe2x80x9cblind rivetxe2x80x9d. EP 0 302 128 B1 discloses a tool for the pulling or setting of blind rivets. For use of such tool, a preliminary borehole and insertion of the blind rivet are still required.
WO 95/05255 discloses a device for production of a riveted joint with pneumatically driven means for the filing of a rivet through the workpieces to be joined and pneumatically driven means for the subsequent pulling of the rivet. The means for the firing of the rivet in this case incorporate a conically tapering, hollow cylindrical driving-in part on the striking head of the rivet jacket. The rivet pin is guided through an opening in the striking surface of the driving-in part which is turned toward the striking head of the rivet in the interior of the driving-in part, and at that pint is picked up by the means arranged to the rear of the driving-in part in the firing direction for the pulling of the rivet. The outlay for construction required by the arrangement of the means for the pulling of the rivet within the hollow cylindrical volume formed by the means for the firing of the rivet is considerable for such a device, especially because it requires the maintenance of small manufacturing tolerances for the means for pulling the rivet. Also, this arrangement requires a large structure for the entire assembly.
GB-A-1,128,442 discloses a device for producing a riveted joint with means for the driving of a rivet having a rivet jacket and a rivet pin guided through the rivet jacket through workpieces to be joined and with means for the pulling of the rivet. The means for the driving-in of the rivet act on the rivet pin, and have a firing bolt in a cylindrical part and a cylindrical striking member arranged between the rivet and the firing bolt, which has a shoulder on which the firing bolt impacts. During insertion into the device, the rivet with its rivet pin is guided in insufficiently far to form contact on a contact strip of the striking member and/or through the manipulation of the device. The movements of the rivet pin connected with the device is moved away from the contact strip. During the driving-in process, an impact of the striking member occurs on the rivet pin. This impact frequently leads to an undesired deformation of the rivet pin and/or to damage of the striking member.
DE 295 14 392 U1 discloses a rivet in which the rivet jacket is stopped on the rivet pin. Especially, the rivet jacket is stopped between convexities constructed between the rivet pin and the rivet head. The rivet pin has a conical point on its first end turned toward the workpieces. With driving in of such rivet, the driving-in force is exerted on the rivet jacket. Using such rivet with the disclosed device in which the means for the driving-in of the rivet work on the rivet pin, the rivet pin is forced through the rivet jacket, whereupon no riveted joint can be produced.
Objects of the present invention are to provide a device for producing a riveted joint which overcomes the drawbacks of conventional devices and which prevents the deformation of the rivet pin and/or of the striking member, and thus, provides a higher level of operational security and a longer life of the device.
Other objects of the present invention are to provide such device to be produced at low cost and guaranteeing reliable operation. The outlay for the construction for the preparation of the means for the pulling and means for the firing of the rivet is thus to be as small as possible, and especially with as small as possible structural dimensions. Also, a rivet which can be processed using this device is to be prepared for use.
The foregoing objects are basically obtained by a device where its striking member is held in axial contact on the rivet pin in the cylindrical part by a flexible element, especially by a first helical spring. This arrangement provides the advantage that the striking member already engages on the rivet pin when the firing bolt impacts on the striking member. Thus, any damage, particularly bending, of the rivet pin and of the striking member is reliably prevented on the basis of an impacting of the striking member on the rivet pin. Furthermore, a dropping of the torn-off rivet pin into the firing channel is prevented. The device can be operated in any position. Particularly, rivets can even be arranged facing vertically upward.
Since the means for the driving-in or firing of the rivet act on the rivet pin, the means for the pulling of the rivet can advantageously engage in the firing direction before the means for the firing of the rivet on the rivet pin. The constructive configuration of space allowed for the realization of the means for pulling the rivet is thus greater, and a corresponding device of small dimensions can be easily realized. The firing of the rivet with acting upon the rivet pin then increases the reliability of the riveted joint being produced, since a certain penetration of the workpieces to be joined is guaranteed by means of the rivet pin. The means for the firing and means for the pulling of the rivet can be powered pneumatically, hydraulically, magnetically, electrically, piezoelectrically or with use of some means of explosion.
By the xe2x80x9cinterpositionxe2x80x9d of a cylindrical striking member between the firing bolt and the rivet, the reliability of the firing process, and with that the reliability of the riveted joint itself, is heightened. The striking member can then be made up of a first segment with diameter adapted to the diameter of the firing channel and a second segment with smaller diameter adapted to the diameter of the rivet pin. Particularly, the second segment can be of approximately identical diameter up to 1.5-times the diameter of the rivet pin.
The reliability of the firing process is even further heightened by having the centering device adapted to the trough-like or depressed shape of the end of the rivet pin which is adjacent to the striking member. Of particular importance, the traditionally desirable rectangular alignment of the rivet pin in relation to the workpieces to be joined and the corresponding guiding of the rivet during the firing process is guaranteed.
The movement of the striking member at the end of the firing process is smoothly suppressed by the flexible buffer element and especially does not impinge on the end of the preferably metallic firing channel. The service life of the device is thus significantly increased. The buffer element engages preferably on an annular shoulder at the end of the firing channel, which is formed by an opening in the firing channel. For example, the buffer element can be a helical spring, disk spring or rubber or plastic washer.
The firing channel can be made easily accessible as a result of the two-part configuration of the firing channel being formed by a hollow piston and a connecting member which preferably are screwed together. In that case, the striking member can be exchanged when necessary.
The guiding of the rivet pin during the firing and pulling process can be obtained through the end piece. Also, the end piece simultaneously executes a spreading of the clamping jaws during the firing process. Such action allows a friction-free passage of the rivet pin and, if necessary, of the striking member through the clamping jaws during the firing process. Any damage to the clamping jaws and potentially to the striking member is simultaneously and reliably prevented by the rivet pin during the firing process. Also, the introduction of a new rivet is simplified by the spreading of the clamping jaws. The second flexible element can be configured as a helical spring. Alternatively, for example, a disk spring or a rubber or plastic washer can be used.
The piston, joining member and clamp sheathing can be connected with one another, preferably by being screwed together with one another. A pulling of the rivet pin by means of the stress of the pressure of the piston counter to the force effect of a flexible element, preferably a helical spring with high elasticity constant, a reliable pulling of the rivet, and with that a reliable production of the riveted joint, are then guaranteed. The pressure is preferably applied by using hydraulic pressure in order to generate the required high pressure forces.
The device can require only one auxiliary connection, in the form of a compressed air connection. The hydraulic pressure is generated through a pneumatic/hydraulic pressure converter. The rivet is fired pneumatically. The rivet is pulled hydraulically. The entire riveting process including firing and pulling is controlled by a three-stage pneumatic switch element. The pneumatic/hydraulic pressure converter, the same as the rapid evacuation valve, is preferably mounted in a handle of the device.
A rivet can be provided for use in the device according to the present invention. With the pyramid-shaped point of the rivet pin, for example, four cutting edges are formed and simplify penetration of the workpieces. By the provision of catch means directed toward the point of the rivet, any relative movement of the rivet relative to the rivet jacket, especially during the firing process of the rivet, is reliably prevented. The catching means could, for example, be realized by pins projecting radially and distributed around the periphery of the rivet pin, or by truncated conical partial segments of the rivet pin produced by rollers and arranged in axial alignment one behind the other.
Since the rivet jacket is connected tightly with the rivet pin, and preferably is extruded thereon, the rivet pin will not be moved, or at least will not be moved remarkably relative to the rivet jacket during the firing process with use of the rivet in a device according to the present invention. With the device according to the present invention, the means for firing the rivet act on the rivet pin. The rivet pin is preferably of steel or stainless steel. The rivet jacket can likewise be of steel or stainless steel, or alternatively of an aluminum or copper alloy. Upon deformation of the pint, penetration of the workpieces is still possible even when using low firing energy. The point can be configured conical or, if desired, can be ogival. Especially the point can also have one or more cutting edges. The point angle is preferably configured in a range of 30 to 60xc2x0.
The cooperation with the centering device on the striking member is specifically guaranteed by the tapering second end of the rivet pin. A configuration of the second end in the shape of a pyramid is advantageously obtained by suitable separation of a rivet pin from a rod-shaped starting material.
Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.